disas/riscv.c: rvv: Add disas support for vector instructions

disas/riscv.c: rvv: Add disas support for vector instructions

Tested with https://github.com/ksco/rvv-decoder-tests

Expected checkpatch errors for consistency and brevity reasons:

ERROR: line over 90 characters
ERROR: trailing statements should be on next line
ERROR: braces {} are necessary for all arms of this statement

Signed-off-by: Yang Liu <liuyang22@iscas.ac.cn>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20220928051842.16207-1-liuyang22@iscas.ac.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>